The origin of Terce, like that of Sext and None, to which it bears a close relationship, dates back to Apostolic times. As has already been stated (see NONE) according to an ancient custom of the Romans and Greeks, the day and night respectively were divided into four parts of about three hours each. The second division of the day hours was that of Terce from nine o'clock until midday. These divisions of the day were also in vogue among the Jews at the time of Christ. In the New Testament we find mention of the sixth hour in Matt., xx, 5; xxvii, 45; Mark, xv, 33; John, xix, 14; of the ninth hour, in Matt., xxvii, 46; Mark, xv, 25; the Holy Ghost descends upon the Apostles on the day of Pentecost at the third hour, Acts, ii, 15. Some of these texts prove that these three hours were, in preference to others, chosen for prayer by the Christians, and probably also by the Jews, from whom the Christians appear to have borrowed the custom. We find frequent mention in the Fathers of the Church and the ecclesiastical writers of the third century of Terce, Sext, and None as hours for daily prayers. For example, Tertullian, Clement of Alexandria, and the Canons of Hippolytus (see Clement, "Stromat.", VII, vii, in P.G., IX, 455-458). Tertullian says expressly that we should always pray, and that there is no prescribed time for prayer, but adds: "As regards the time, there should be no lax observation of certain hours—I mean, of those common hours which have long marked the divisions of the day, the third, the sixth, and the ninth—and which we may observe in Scripture to be more solemn than the rest" (De Orat., XXXIII, xxv, in P.L., I, 1191-1193).

Clement and Tertullian in these passages refer only to private prayer at these three hours. The Canons of Hippolytus also speak of these three hours as suitable for private prayer. However, on the days called "days of station", that is to say Wednesday and Friday, which were set apart as especially consecrated to prayer, and Sunday, these hours were recited in public (Canon, xx, xxvi). St. Cyprian remarked that these three hours had been observed in the Old Testament, and that Christians should also observe them (De Oratione, XXXIV, in P.L., IV, 541). In the fourth century the custom of praying at these hours became more frequent, and even obligatory, at least for monks (see the texts of the Apostolic Constitutions, of St. Ephrem, of St. Basil, of the author of "De Virginitate" quoted in Bäumer-Biron, "Histoire du bréviaire", 116, 121, 129, 186). Our texts say nothing as to what were the elements of the prayer of Terce, Sext, or None before the fourth century. Doubtless, like all prayers at that time, they were composed of psalms, canticles, hymns, and litanies. It is from the fourth century onwards that we can gather a more precise idea as to the composition of the hour of Terce. In the fourth century, as we have said, the custom of prayer at Terce spread, and tended to become obligatory, at least for monks. There is no mention in the "Peregrinatio ad Loca Sancta" of an office of Terce on ordinary days. Some authors have misunderstood the text here, but there is no mention of a meeting at this hour, except on Sunday and during Lent (see Cabrol, "Etude sur la Peregrinatio Silviæ", Paris, 1895, p. 45, 46). The hour of Terce is also mentioned in St. Jerome, "Ep. ad Lætam." in P.L., XXII, 875; "Ep. ad Eustoch." in P.L., XXII, 420; in the Life of St. Melania the Younger, "Analecta Bollandiana", VIII, 1889, p. 16; in Cassian, "De institut. coenob.", in P.L., LXIX, 112, 126, etc.

At this period it is composed of the same elements as the hours of Sext and None; the distribution is the same, and it is clear that the three "little hours" were composed at the same time and that they have the same origin. The psalms of Terce are different from those of the other two hours. There were also certain varieties of composition. Thus, in certain countries, three psalms were assigned to Terce, six to Sext, nine to None, in virtue of the symbolism.

The composition varies also in the various liturgies. In the Greek Church Terce is composed of two parts, each made up of psalms (two for the first, three for the second), with invitatory, troparia, and final prayer. (See Neale and Littledale, "Commentary on the Psalms", I, p. 34.) In the Benedictine Rite, Terce comprises, on week days, the Gradual Psalms, 119, 120, and 121, with a capitulum, verse, Kyrie, Pater, and prayer. On Sundays and Mondays the Gradual Psalms are replaced by three octonaries (i.e. three sections of eight verses each) of Psalm cxviii. In the Mozarabic Rite, three octonaries of Ps. cxviii are also recited, the composition otherwise differing very little. In the main, the recitation of three psalms at Terce, as at the other two "little hours" of the day, is founded on a universal and very ancient tradition. Divergencies on this point are only exceptional. The practice of the Roman Liturgy, which at first sight appears to be somewhat different, may be traced to this tradition also. In this rite a part of Ps. cxviii is recited at Terce as well as at the other "little hours", the psalm being divided into three double octonaries. After the new Psalter arranged in 1911-12, the psalms are: on Sunday, Ps. cxviii (three divisions); on Monday, Ps. xxvi (two divisions); on Tuesday, Ps. xxxix (three divisions); on Wednesday, Ps. liii (two divisions); on Thursday, Ps. lxxii (three divisions); on Friday, Ps. xxxix (two divisions); on Saturday, Ps. ci (three divisions). The number three is therefore preserved in each case. The hymn "Nunc Sancte nobis Spiritus" recalls the descent of the Holy Ghost upon the Apostles. The other elements are the same as for Sext and None.

The Fathers of the Church and the liturgists of the Middle Ages considered the hour of Terce as corresponding to the hour of Christ's condemnation to death. They also often point out on this occasion the mysteries of the number three, which in ecclesiastical symbolism is a sacred number (see Bona, loc. cit.). What gives it its especial dignity, however, is its association with the descent of the Holy Ghost upon the Apostles on the day of Pentecost at this very hour ("seeing it is but the third hour of the day", Acts, II, 15). In several liturgies, and particularly in the Roman, this connection is brought to mind by one or other of the formulæ. Again, this is the reason why, from the earliest times, the hour of Terce was chosen as that of the Mass on feast days. Sometimes, also, this hour is called in liturgical language hora aurea or hora sacra (see Durandus, "De rit. eccles.", c. viii).